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113 CHAPTER 29: HUMAN DEVELOPMENT AND AGING Chapter Overview Introduction Chapter 29 explores the life cycle of human beings from conception to death. All the cells come from that first single cell, but through a complex series of interactions and differentiations of cells, we arrive at the stunningly intricate human machine. As we pass through our life cycle, stepwise changes take place to prepare us for the probable demands of the moment. Eventually, by means not entirely clear, we arrive at the end of life. Key Concepts Here are some concepts that students should have a better understanding of after reading this chapter: sperm advancement from the vagina to the uterine tubes for fertilization and capacitation; the completion of meiosis II in the egg; the processes of implantation and embryogenesis; trophoblastic nutrition and the roles of the placenta; the names and functions of the embryonic membranes; the origins of the organs from the primary germ layers; the major stages of prenatal development: pre-embryonic, embryonic, and fetal; the major events within the stages of prenatal development; the activities of the neonate key to transition to infant life: changes in the circulatory patterns, inflation of the alveoli, thermoregulation, and fluid balance; the challenges presented by premature infants; factors causing congenital anomalies such as infectious diseases, teratogens, mutagens and genetic disorders; aging phenomena and senescence in specific organ systems; importance of nutrition and exercise in delaying senescence; an understanding of major hypotheses explaining the mechanisms of senescence; the means of determining brain death; and the technology of producing babies in the laboratory. Topics for Discussion 1. Folic acid is necessary to help prevent neural tube defects in the first trimester, often before the woman knows she is pregnant. Therefore, folic acid supplements have sometimes been added in orange juice and milk. Students who could become pregnant are advised to “take folic before they frolic!” 2. Students may be interested in the case of thalidomide. This was a medication prescribed in some European countries to reduce morning sickness in pregnant women. Unfortunately, it seems to have caused significant birth defects (see Fig. 29.12). It is now being prescribed for AIDS patients. 3. How can it be that the mother’s body allows the cytotrophoblast to grow into the endometrium? The body should cast it out as the (partly) foreign invader that it is. 4. Recently it has become possible to clone large mammals using the nucleus of an adult to produce an identical genetic twin several years younger than the original. What ethical implications does this have? Will people have themselves cloned so as to harvest new organs from the resulting fetus? Often, science advances faster than our legal code does. 5.
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This note was uploaded on 02/09/2012 for the course BIO 102 taught by Professor William during the Spring '11 term at Harvard.

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